SECTION II.-QUANTITY NECESSARY FOR HEALTH

AND OTHER PURPOSES.

A healthy adult requires daily from 70 to 100 oz. of water for the processes of nutrition, about one-third of which is contained in articles of diet, the other twothirds being supplied in the form of liquids. The amount for cooking has been estimated at from half-agallon to a gallon daily for each person, while the quantity deemed necessary for personal cleanliness and for washing purposes will necessarily vary very much according to the habits of the individual.

Dr. Parkes gives the following quantities used by a man in the middle class :—

The soldier is allowed 15 gallons daily, no extra allowance being given for the women and children in a regiment. In the poorer districts of the city of London, Dr. Letheby found that the amount used was 5 gallons per individual daily, and in model lodginghouses, according to Mr. Muir, 7 gallons. A showerbath daily will require 3 to 4 gallons, while a plungebath will take from 40 to 60 gallons. Where waterclosets are used, an additional allowance of from 4 to 6 gallons must be provided. Latrines require a less

amount.

In gross amounts Professor Rankine gives an estimate of 10 gallons daily per individual for domestic

purposes, 10 for municipal purposes, and 10 more for trade purposes in manufacturing towns, and this amount, large though it seems, is actually supplied to many towns at the present day. Glasgow, for example, receives 35 gallons daily per head of population; Edinburgh and Southampton 35; Paris 31; and Liverpool 30. The different London water companies supply from 21 to 34 gallons, while the manufacturing towns in Lancashire and Yorkshire, according to Mr. Bateman, received from 16 to 21 gallons. Mr. Rawlinson's minimum estimate for manufacturing towns is 20 gallons per head daily.

In apportionating the daily allowance for all purposes, Dr. Parkes has given the following estimate :—

No doubt this estimate of Dr. Parkes may be regarded as somewhat excessive, especially in the items of domestic and water-closet supply, but it has been based on the principle that a liberal allowance is not only necessary for thorough cleanliness, but that it is also required for an efficient clearage of sewers. Many engineers are of opinion that the great waste which is sometimes complained of is owing to waterclosets; and in towns with a constant supply, small cisterns, termed water-waste preventers, have been in

troduced, to permit only a certain amount of water to flow into the pan each time the closet is used. The great objection to them is, that they are generally too small, so that neither the pan nor soil-pipe is thoroughly flushed, and there is the consequent risk of filth-accumulation. Where water is scarce it may be necessary to enforce rigid economy, but where it can be procured plentifully, it is far better that any error in the amount of supply should be on the side of excess.

For hospitals the daily amount per patient may be estimated at about 30 or 40 gallons. In prisons and workhouses the quantity will vary according to the bathing arrangements, and whether water-closets are used. In the Convict Prison, Portsmouth, where water-closets and water-latrines are both in use, and where each prisoner is allowed a general bath once a week, the amount averages about 11 gallons per convict daily.

SECTION III.-MODES OF SUPPLY.

This part of the subject has reference to wells, borings, the collection and storage of water, and to water-works generally.

1. Wells and Borings.-Most surface wells are sunk into a bed of sand or gravel resting upon an impermeable stratum of clay. If the surface of the clay basin is very irregular, as is commonly the case, it is impossible to predict at what depth the water will be reached, or at what level it will permanently stand. Theoretically, it may be inferred that the superincumbent stratum of sand or gravel is situated below the level of the lowest point at which the water can escape from the clay basin; and hence, in digging such wells,

it is only necessary to reach the line of saturation to find water.

In sparsely populated districts these surface wells constitute the usual source of supply, and if proper precautions be taken to guard against the soakage of animal excreta into them, they usually yield a wholesome water; but in villages and towns the soil often becomes so saturated with impurities that it is next to impossible to prevent their pollution. In crowded localities, therefore, they should always be regarded with suspicion, and, as far as possible, their use should be discontinued. Deep wells, on the other hand, are not open to this objection, because they are generally sunk through an impervious stratum, which prevents the infiltration of any surface impurities, and at the same time serves to keep down the water in the porous strata beneath. The quality of the water from these wells, as has already been shown, will depend on the nature of the geological formation of the district. It is also apparent that, in accordance with a well-known physical law, it is only necessary to bore through the impervious stratum, and reach the water-bearing bed, for the water to rise to the surface, or to within a short distance of it, so as to be collected in a well of ordinary dimensions. Indeed, in certain low-lying districts, where a boring is made at a point considerably below, the level of the line of infiltration into the water-bearing stratum, the water rises above the surface and overflows. Such overflowing wells, or artesian wells, as they are called, were once common in the valley of the Thames, and are still to be met with in the flat lands of Essex and on the coast of Lincolnshire. Ordinary borings differ from artesian wells in not piercing through a retentive stratum in

order to reach the water-supply. They are very common in the chalk and new red sandstone districts, and are made to increase the yield of the wells. Practically, it is found that one boring adds to the supply of a well nearly as much as several. Thus in the Bootle well at Liverpool, with 16 bore-holes, some of which were 600 feet deep, Mr. Stephenson found that when all were plugged up but one, the yield was 921,192 gallons per day, and when all were open it was only increased by 112,792 gallons.

Deep wells are now being abandoned for the supply of large towns, because they are found to be insufficient for the wants of a growing population, and obviously cannot be multiplied within a given district beyond certain limits, because every single well drains a surrounding area of some considerable extent. For large isolated buildings, however, such as lunatic asylums, workhouses, and prisons, they usually supply the whole of the water required; and in selecting a site in the country for any such building, the possibility of obtaining the requisite water-supply, and the cost at which it can be procured, are points of the first importance.

Generally speaking, the chance of obtaining a good supply will depend upon the nature of the underlying strata, and upon the level of the proposed site. Wells sunk in superficial sand or gravel beds, though yielding a good supply at ordinary times, are very liable to have their yield very much lessened in seasons of drought, unless they are situated at points considerably below the level of the surrounding country, and the same remark applies to wells in the chalk districts. On the other hand, wells or borings in the new red sandstone and limestone formations usually yield a large and constant